The invention relates to continuous solidification of radioactive liquid waste.
The invention described herein was made in the course of, or under, a contract with the U.S. Energy Research and Development Administration.
Calcination of high level radioactive waste using fluidized bed techniques has been generally investigated. As used herein, "high-level radioactive liquid wastes" refers to those aqueous wastes resulting from the operation of a first cycle solvent extraction system, and the concentrated wastes from subsequent extraction cycles in a facility for reprocessing irradiated nuclear reactor fuels. These wastes may contain virtually all of the nonvolatile fission products, several tenths of one percent of the uranium and plutonium originally in the spent fuels, and all the other actinides formed by transmutation of the uranium and plutonium as normally produced in a nuclear reactor.
The processes resulting from previous investigations have been apropos for some specific applications, but had inherent limitations or disadvantages for other applications such as where continuous waste solidification was required. For example, prior art processes for calcining liquid radioactive waste in a fluidized bed reactor may have one or more of the following limitations:
A HIGH INVENTORY OF FISSION PRODUCTS IS MAINTAINED IN THE CALCINER BED RESULTING IN DECAY HEAT PROBLEMS;
CONTINUOUS OPERATION MAY NOT BE FEASIBLE BECAUSE OF THE REQUIREMENT OF "ART" OR OPERATOR CONTROL STEPS PECULIAR TO THE PROCESS FOR WHICH THERE CANNOT BE AN AUTOMATIC COMPENSATION;
PREVIOUS BEDS MAY NOT ACHIEVE EQUILIBRIUM WITHIN SHORT TIME SPANS AND THEREFORE REQUIRE A LONG WAITING PERIOD FOR BED TURNOVER;
OPERATION IN SOME PROCESSES WAS LIMITED TO TEMPERATURES BELOW ABOUT 400.degree. C because the bed material had a low melting composition, and the resulting product had a high nitrate and water concentration;
PRIOR ART PROCESSES GENERALLY DO NOT PERMIT SUCCESSFUL CALCINATION OF SODIUM BEARING WASTES WITHOUT SIGNIFICANT ADDITION OF FEED ADDITIVES;
AND, FINALLY, WHEN PRIOR ART PROCESSES ARE ADJUSTED OR MODIFIED TO ELIMINATE ONE OR ANOTHER OF THE RECITED LIMITATIONS, THE RESULTANT PRODUCTS MAY HAVE INFERIOR OR UNDESIRABLE VITRIFICATION PROPERTIES.